This invention relates to papermakers fabrics or felts intended for use in the watering sections of a papermakers machine. This invention relates particularly to channel type or cabled papermakers felt for use in the press or dewatering section of a papermakers machine.
It has been recognized for some time that it would be advantageous to have a papermakers felt having channels or voids for directing the water removed from the paper slurry away from the papermakers felt so as to prevent rewetting of the slurring. There have been various attempts to accomplish this by using batt on base type fabrics. In more recent attempts to produce a papermakers felt having improved drainage properties, prior art has attempted to secure cable or drainage yarns to the base of a fabric by use of adhesives, see U.S. Pat. No. 3,616,258; and to secure cable or drainage yarns to the running surface of the fabric by means of stitch or bindery yarns, see U.S. Pat. No. 4,187,618.
The difficulty with prior art attempts to produce a fabric having improved drainage qualities has been the failure of the fabrics to indure sustained running periods and to indure the riggers of papermakers machinery. In the case of the adhesive held cable yarns it has been found that the adhesive may become cracked, brittle or fragmented and thereby lose control over the cable yarns. The prior art attempts to use binder yarns have run into difficulty in that the binder yarns may be subject to extreme conditions in the papermaking machinery and therefore become frayed and lose control of the cable yarns. Due to the nature of binder yarns which limits the number of yarns which were inserted in a fabric in order to maintain the desired porosity the fatigue of the binder yarn can cause some difficulty.